CHICAGO — Attorney General Eric Holder on Monday presented the Obama administration’s most detailed justification for armed drone strikes against Al Qaeda leaders, arguing that the U.S. government doesn’t legally need judicial review to kill terrorist operatives overseas — even when they’re Americans.

“It’s clear that United States citizenship alone does not make such individuals immune from being targeted. But it does mean that the government must take into account all relevant constitutional considerations with respect to United States citizens — even those who are leading efforts to kill innocent Americans,” Holder said in a speech delivered at Northwestern University School of Law.

Questions about the legal basis for lethal U.S. drone operations have swirled for years, particularly as the Obama administration stepped up drone strikes in Pakistan. However, the queries and criticism became more intense after reports in 2010 that a New Mexico-born cleric, Anwar al-Awlaki — killed in a Sept. 2011 drone strike — was on a list of terror suspects that the U.S. had decided to target using deadly force.

Holder is the highest-ranking administration official yet to defend the administration’s position, arguing that placing terror suspects on a so-called kill list is subject to “robust oversight” but should not and need not involve the courts.

“Some have argued that the president is required to get permission from a federal court before taking action against a United States citizen who is a senior operational leader of Al Qaeda or associated forces. This is simply not accurate,” Holder said. “Due process and judicial process are not one and the same, particularly when it comes to national security. The Constitution guarantees due process, it does not guarantee judicial process.”

Holder’s half-hour speech came in the wake of months of internal administration debate about how to respond to calls for the release of a still-secret Justice Department legal opinion justifying the use of deadly force against al-Awlaki. The address appeared to reflect a decision to shed some more light on the legal standards the administration applies in such cases but stopped short of the transparency demanded by many critics and even some supporters of the policy.

Al-Awlaki’s father filed a lawsuit in 2010 challenging the targeted-killing policy, but U.S. District Court Judge John Bates dismissed the case, saying courts were unsuited to make the judgments involved in singling out terrorists for death.

However, Bates said the suit presented “stark, and perplexing, questions” and called his own dismissal of it “somewhat unsettling.” The judge noted that if the U.S. government wanted to wiretap al-Awlaki’s phone calls, even in Yemen, a court-issued warrant would be required, but to kill him required no judicial warrant or review.

In his speech, Holder rejected claims by some legal scholars and human-rights groups that the use of lethal force off the battlefield must be limited only to instances of imminent threat, such as cases in which authorities have indication that a terror suspect is in the midst of plotting a specific attack.

Al Qaeda “leaders are continually planning attacks against the United States and they do not behave like a traditional military — wearing uniforms, carrying arms openly or massing forces in preparation for an attack,” Holder said. “Given these facts, the Constitution does not require the president to delay action until some theoretical end-stage of planning — when the precise time, place and manner of an attack become clear. Such a requirement would create an unacceptably high risk that our efforts would fail and that Americans would be killed.”

Holder said lethal force should not be used when it’s “feasible” to capture a terror suspect, but his argument on that point didn’t shed much light on where that line is drawn. He said the factors include whether there’s enough time to capture a suspect and whether that can be done “without undue risk to civilians or to U.S. personnel,” but what level of danger to troops is “undue” was far from clear.

Holder said the legal standards for the use of drones were no different than those that apply to other tools in the military’s arsenal.

“These principles do not forbid the use of stealth or technologically advanced weapons. In fact, the use of advanced weapons may help to ensure that the best intelligence is available for planning and carrying out operations, and that the risk of civilian casualties can be minimized or avoided altogether,” Holder said.

While more expansive than previous administration explanations, Holder’s address left some important questions unanswered about the administration’s policy on lethal force. He did not say, for instance, whether a propagandist or inspirational figure who recruits terrorist operatives but is not directly involved in planning specific attacks could be a legitimate target for deadly force.

Holder also gave little insight into who participates in the process for approving the use of deadly force and made no mention of the Central Intelligence Agency or its role in running many of the drone operations. He also did not say directly whether Congress would be notified in advance prior to an effort to kill an American.

“There was no description of the internal process — no nuts and bolts,” said Robert Chesney, a law professor at the University of Texas. “The missing part was a full-on account of exactly what the internal screening process is, but I’m not surprised that half got dropped out.”

Some experts said being more specific about the precise standards could give some terrorists a kind of immunity from attack.

“I can’t imagine that one would want to wind up revealing the contours of that in any way that would satisfy the rights’ groups. It would allow the gaming of the system,” said Kenneth Anderson, a law professor at American University.

Anderson praised the address, declaring that “presidents two decades from now will be citing to this speech, I believe, or at least their top national security leaders and lawyers. It was also very careful not to limit a future president’s ability to deal with new situations.”

However, critics of the targeted-killing policy complained that Holder’s speech broke little new ground in terms of new arguments justifying drone strikes under international law.

“The three core arguments that he basically made to the world for why we can fire Hellfire missiles at countries we’re not at war with we’ve heard before,” said Mary Ellen O’Connell, a professor at Notre Dame’s law school. “He just recycled these inadequate arguments. That’s pretty disappointing. … I don’t understand why they think these lame arguments can support a policy that is unsupportable.”

Although targeted killing and U.S. drone operations are controversial in international law circles, the Obama administration’s approach appears to have broad support among the American public.

An overwhelming 83 percent of Americans back the administration’s use of armed drones, according to a Washington Post/ABC News poll last month. Support dropped to 65 percent when a U.S. citizen is the target of the strike, but only 26 percent said they’re opposed to using drones against American terror suspects, the poll found.

Many political figures from both major parties have also endorsed the administration’s approach. However, Republican presidential candidate and libertarian stalwart Rep. Ron Paul of Texas called the killing of al-Awlaki a step toward “tyranny.”

“This is obviously a step in the wrong direction,” Paul said a few days after the drone strike that killed al-Awlaki. “We have just totally disrespected the Constitution.”

On Friday, when Northwestern announced Holder’s speech, the school said Dean Daniel Rodriguez would ask the attorney general a series of questions submitted by the audience. However, a few hours before Holder spoke Monday, a university spokeswoman said the Q-and-A session would not be taking place.

A Justice Department spokeswoman said the length of Holder’s remarks left no time for questions. That decision may have dodged some public contention over the administration’s policy, judging by the comments of Northwestern law students interviewed after the speech.

Second-year student Jaya Gupta complained of a “circularity” to some of Holder’s arguments.

Holder “said due process is not judicial process, but we don’t really know what it is. He didn’t do much to tie it to the over 200 years of jurisprudence that has been developed,” Gupta said.

“He said that due process can be nonjudicial, but it cannot be,” said Russell Sherman, a third-year law student. “It was all about advocating against checks and balances. All in all, I thought it was pretty scary stuff.”

Second-year law student Zach O’Dell complained that Holder flatly declared that the U.S. is in an armed conflict with Al Qaeda. “That assumption is patently incorrect,” O’Dell said.

O’Dell also faulted the attorney general’s remarks about the U.S. only using deadly force against a U.S. citizen when capture isn’t “feasible.”

“That was a trick because it does not elucidate the standard at all and seems sort of tautological,” O’Dell said, adding, “I was disappointed he didn’t take questions.”